CtIP mediates replication fork recovery in a FANCD2-regulated manner.

Area of Science:

• Molecular Biology
• Genetics
• DNA Repair

Background:

• Fanconi anemia (FA) is a genetic disorder linked to chromosome instability and cancer.
• The FA pathway, involving FANCD2, is critical for repairing stalled replication forks.
• Homologous recombination (HR) proteins are implicated in replication fork recovery.

Purpose of the Study:

• To investigate the role of CtIP in the replication stress response.
• To identify novel interaction partners of FANCD2.
• To elucidate the mechanism of replication fork recovery involving FANCD2 and HR proteins.

Main Methods:

• Co-immunoprecipitation to identify protein interactions.
• Chromatin immunoprecipitation (ChIP) to assess protein localization.
• Cellular treatments with replication inhibitors (e.g., aphidicolin).

Main Results:

• CtIP was identified as a novel binding partner of FANCD2.
• CtIP binds and stabilizes FANCD2 independently of FANCD2 ubiquitination.
• FANCD2 recruits CtIP to stalled replication forks, where they cooperate for fork restart and origin firing suppression.
• BRCA1 regulates the recruitment of MRE11, FANCD2, and CtIP to stalled forks.

Conclusions:

• CtIP is a novel player in the replication stress response, acting downstream of FANCD2.
• The FANCD2-CtIP interaction is essential for replication fork stability and restart.
• BRCA1 orchestrates the assembly of a protein complex including MRE11, FANCD2, and CtIP to ensure genome stability.